Linear motor system with powered curvilinear track sections

ABSTRACT

A method for manufacturing a curvilinear track section including: forming a curvilinear track portion; cutting out a first slot grouping from an exterior edge of the curvilinear track portion, wherein the first slot grouping is at a first predetermined angle; cutting out a second slot grouping from the exterior edge of the curvilinear track portion, wherein the second slot grouping is at a second predetermined angle; and inserting motor units into the first and second slot groupings. A curvilinear track section having: a curvilinear track portion; a first slot grouping formed in an exterior edge of the curvilinear track portion, wherein the first slot grouping is at a predetermined angle relative to the exterior edge; a second slot grouping formed in the exterior edge of the curvilinear track portion, wherein the second slot grouping is at a second predetermined angle; and motor units inserted into the first and second slot groupings.

RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser.No. 62/006,583 filed on Jun. 2, 2014 which is incorporated herein byreference.

FIELD

The present disclosure relates generally to linear motor systems. Moreparticularly, the present disclosure relates to a linear motor systemwith powered curvilinear track sections.

BACKGROUND

Conventional linear motor systems may be constrained where there arecurvilinear or curved sections of track for various reasons. Forexample, as the radius of the curved section is smaller towards theinterior of the curve than the exterior of the curve, conventionallinear motor systems and, in particular, linear motor conveyor systems,may encounter problems with the arrangement and configuration of theirmotor coils through the curve.

Further, conventional linear motor systems with curvilinear or curvedsections of track may produce unwanted forces on a moving elementtraversing a curved track section. For example, the unwanted forces maybe caused by undesirable rates of change of acceleration, often called“jerk”, as the moving element moves through the curve. This “jerk” canlead to instability of the moving element and any objects on the movingelement, such as a workpiece, fixtures, or the like.

Conventional linear motor systems may also have difficulty trackingmoving elements when the moving elements traverse a curvilinear orcurved section of track and/or during transition to straight sections oftrack.

As such, there is a need for an improved curvilinear track section forlinear motor systems.

SUMMARY

In one aspect, there is provided a method for manufacturing acurvilinear track section of a linear motor system, the method includes:forming a curvilinear track portion into a suitable shape; cutting out afirst slot grouping from an exterior edge of the curvilinear trackportion, wherein the first slot grouping is at a first predeterminedangle relative to the exterior edge of the curvilinear track portion;cutting out a second slot grouping from the exterior edge of thecurvilinear track portion, wherein the second slot grouping is at asecond predetermined angle relative to the exterior edge of thecurvilinear track portion; and inserting motor units into the first andsecond slot groupings.

In a particular case, each of the first and second slot groupings mayinclude pairs of slot groupings and the pairs of slot groupingsinterleave.

In another particular case, the curvilinear track portion and the firstand second slot groupings may be configured to provide a sinusoidalangular velocity profile for moving elements on the curvilinear tracksection.

In still another particular case, the curvilinear track portion may haveat least one region with a clothoid profile. In some cases, this regionmay be a transition region.

In yet another particular case, the cutting out of the first group ofslots and the second group of slots may be by stamping, laser cutting,or water jet cutting.

In yet another particular case, slots within each slot grouping may havedifferent slot depths.

In a particular case, the depth of each slot may depend on the angle ofthe slot relative the exterior edge of the curvilinear track portion.

In another particular case, the depth of the slot may be configured toreceive a motor unit.

In still another particular case, the depth of the slot on one end ofthe first slot grouping and the depth of the slot on another end of thefirst slot grouping are approximately equal to the depth of a straightsection of the linear motor system and the depths of the slots inbetween are deeper.

In another aspect, there is provided a curvilinear track section of alinear motor system having: a curvilinear track portion having apredetermined curved shape; a first slot grouping formed in an exterioredge of the curvilinear track portion, wherein the first slot groupingis at a predetermined angle relative to the exterior edge of thecurvilinear track portion; a second slot grouping formed in the exterioredge of the curvilinear track portion, wherein the second slot groupingis at a second predetermined angle relative to the exterior edge of thecurvilinear track portion; and motor units inserted into the first andsecond slot groupings.

In a particular case, each of the first and second slot groupings mayinclude pairs of slot groupings and the pairs of slot groupingsinterleave.

In another particular case, the curvilinear track portion and the firstand second slot groupings may be configured to provide a sinusoidalangular velocity profile for moving elements on the curvilinear tracksection.

In still another particular case, the curvilinear track portion has atleast one region with a clothoid profile.

In yet another particular case, slots within each slot grouping may havedifferent slot depths.

In still yet another particular case, the depth of the slot may dependon the angle of the slot relative the exterior edge of the curvilineartrack portion.

In a particular case, the depth of the slot on one end of the first slotgrouping and the depth of the slot on another end of the first slotgrouping may approximately equal to the depth of a straight section ofthe linear motor system and the depths of the slots in between aredeeper.

In still another particular case, the curvilinear track section mayinclude a plurality of sensors positioned on the curvilinear tracksection, wherein the sensors are oriented perpendicular to the directionof motion.

In a particular case, a first sensor of the plurality of sensors may becalibrated based on the calibration of a last sensor on a straight trackportion immediately preceding the curvilinear track selection.

In another particular case, the curvilinear track section may include acontroller configured to provide a boost to a selected motor unit when amoving element approaches an apex of the curvilinear track section.

In another aspect, there is provided a wedge aligner for a linear motorsystem, the wedge aligner including: a fixed mount configured to rigidlyattach to a first track section of the linear motor system and flexiblyattach to a second track section; a wedge configured be inserted betweenthe flexibly attaching portion of the fixed mount and the second tracksection; and an adjustor provided to the wedge configured to translatethe wedge back and forth along the longitudinal axis of the first andsecond track sections in order to compensate for stack-up tolerances.

BRIEF DESCRIPTION OF FIGURES

Embodiments of the present disclosure will now be described, by way ofexample only, with reference to the attached Figures.

FIG. 1 illustrates a perspective view of a track section of a linearmotor conveyor system;

FIG. 2A illustrates a perspective view of the track section;

FIG. 2B illustrate an exploded view of coils of the track section;

FIG. 2C illustrates an exploded view of the track section;

FIG. 3 illustrates a perspective view of a track section with acurvilinear profile;

FIG. 4A illustrates a perspective view of a moving element 104;

FIG. 4B illustrates a perspective view of a moving element 104 separatedfrom a machine readable medium;

FIG. 5 is a schematic of a control architecture for a conveyor system,according to an embodiment;

FIG. 6 is a schematic of a control architecture for a conveyor system,according to another embodiment;

FIG. 7A is a top view of a powered curvilinear track section accordingto an embodiment;

FIG. 7B is an expanded top view of a portion of the powered curvilineartrack section of FIG. 7A;

FIG. 7C is an expanded top view of a portion of the powered curvilineartrack section of FIG. 7A with a motor unit;

FIG. 8 is a perspective view of the powered curvilinear track sectionwith stacked laminations;

FIG. 9A is a perspective view of the powered curvilinear track sectionwith motor coils;

FIG. 9B is a top view of the powered curvilinear track section withmotor coils;

FIG. 10A is a top view of a curvilinear track section with sensors,according to an embodiment;

FIG. 10B is a perspective view of the curvilinear track section withsensors;

FIG. 11 is a top view of the curvilinear track section with clothoidprofile, according to an embodiment;

FIGS. 12A and 12B are a top view of two adjacent straight track sectionsjoined using a wedge aligner, according to an embodiment;

FIGS. 13A and 13B are a top view of a straight track sections and acurvilinear track section joined using a wedge aligner, according to anembodiment;

FIG. 14 illustrates a flowchart for a method of manufacturing a poweredcurvilinear track section, according to an embodiment;

FIG. 15 illustrates a flowchart for a method of laying out sensors on acurvilinear track section, according to an embodiment;

FIG. 16 illustrates a flowchart for a method of linearizing sensors on acurvilinear track section, according to an embodiment; and

FIG. 17 illustrates a flowchart for a method of moderating magnetic gapon a curvilinear track section, according to an embodiment.

DETAILED DESCRIPTION

Generally, the present disclosure provides a system and method forpowered curvilinear track sections in a linear motor system or conveyorthat is intended to overcome at least some of the limitations ofconventional linear motor systems.

FIG. 1 illustrates a conveyor system 100 having a track section 102. Thetrack section 102 features one or more moving elements 104 (only one isillustrated) which are configured to ride or travel along a track 106 ofthe track section 102. The moving element 104 may be any appropriatetransport structure and may be configured to carry, support, orotherwise transport a support, such as, for example, a pallet, platform,carriage, staging, bed or the like. The track 106 includes a frame 108configured to support the moving element 104. Some of the principles ofoperation of a similar track section are described in more detail inU.S. Pat. No. 8,397,896 to Kleinikkink et al., which is herebyincorporated herein by reference.

The conveyor system 100 can be composed of a plurality of track sections102 which are mechanically self-contained and quickly and easilyseparable from one another so as to be modular in nature. In thisembodiment, the track sections 102 are mounted on a support (not shown)so as to align and abut one another in order to form a longer track. Inorder to be modular, each track section 102 may house self-containedelectronic circuitry for powering and/or operating the track section102. The conveyor system 100 may include curvilinear track sections 102.

FIG. 2A illustrates a perspective view of the track section 102. FIGS.2B and 2C illustrate an exploded view of the track section 102. Thetrack section 102 includes the frame 108 that houses a linear drivemechanism 110. The linear drive mechanism 110 is formed as a statorarmature 112 including a plurality of embedded coils 114. The embeddedcoils can be individually excited so that an electrically-inducedmagnetic flux produced by the stator armature 112 is located adjacent toa given moving element 104 to be controlled, in a direction normalthereto, without affecting adjacent moving elements 104. The motiveforce for translating each moving element 104 arises from themagnetomotive force (MMF) produced by each moving element 104 and thestator armature 112, i.e., by the tendency of the corresponding magneticfluxes provided by the stator armature 112 and moving element 104 toalign. A controller (described below) enables separate and independentmoving MMFs to be produced along the length of the track section 102 foreach moving element 104 so that each moving element 104 can beindividually controlled with a trajectory profile that is generallyindependent of any other moving element 104. Structurally, the tracksection 102 may thus be broadly classified as a moving-magnet typelinear brushless motor having multiple moving elements 104.

FIG. 2C illustrates a section of track 102 which includes a first guiderail 107 and a second guide rail 109 configured to support the movingelement 104. The first and second guide rails 107, 109 are designed suchthat the moving element 104 may be removed from the track 102 when amagnetic force is overcome. The magnetic force is overcome, for example,where a user pries the moving element 104 away from the track 106. In analternative, the moving element 104 may be removed from the track 106where the magnetic force is reversed, reduced, or removed.

The first guide rail 107 supports the moving element 104 vertically andhorizontally. The first guide rail 107 may have a “V” shaped profile tosupport and guide the moving element 104 on the track 102. The secondguide rail 109 supports the moving element 104 horizontally. The secondguide rail 109 may be a smooth surface with a flat profile.

Referring again to FIG. 1, each moving element 104 includes a shelf 117for carrying various components. The moving element 104 also has anextension 118 provided with a machine readable medium 120 (indicated inFIG. 4), which may be, for example, a magnetic strip, an opticallyreceptive, transmissive or reflective strip, capacitive strip,color-coded strip, other type of feedback system or the like. Theextension 118 is configured such that the machine readable medium 120interacts with sensors 122, 123 provided to the track 106. The sensors122, 123 are configured to read the machine readable medium 120, whethermagnetically, optically, or otherwise. The machine readable medium 120and sensors 122, 123 form a position sensing system. The positionsensing system may be arranged such that the position sensing system isprotected from traffic on the track section 102 and dust and otherdebris. The position sensing system is employed in the moving element104 identification and position-detecting subsystem (described infurther detail below).

The sensors 122, 123 are located on the track section 102 and themachine readable medium 120 is located on the moving element 104. In analternative, the sensors 122, 123 may be located on the moving element104 and the machine readable medium 120 may be located on the tracksection 102. The sensors 122, 123 may be configured to read anidentifier of the moving element 104 from the machine readable medium120. The same sensors 122, 123 are configured to gather data todetermine a relative position of the moving element 104 on the tracksection 102 from the machine readable medium 120.

FIG. 3 illustrates a conveyor system 100 having a curvilinear profile,in accordance with a further embodiment. Where the track section 102 iscurvilinear, the sensors 122, 123 are positioned along the curvilinearprofile such that the machine readable medium 120 can be read by thesensors 122, 123 and the readings can then be translated from thecurvilinear profile to a linear profile, using linear units such asmicrons, for the purposes of feedback control. Control of the movingelement 104 may then occur in the linear profile/linear units.Curvilinear or curved sections of track will be described in furtherdetail below.

FIGS. 4A and 4B show a moving element 104 when removed from the track106. The moving element 104 has the machine readable medium 120 on theextension 118. The machine readable medium 120 is read by the sensors122, 123 to provide data used to determine the moving element 104′sposition as the moving element 104 travels along the track 106. Thisposition feedback is then used to control the movement of the movingelement 104. The moving element 104 has elements 124, such as permanentmagnets, that interact with the stator armature 112 and coils 114 in thecorresponding track section 102 to move along direction 126 of FIG. 1.

The moving element 104 has a first set of bearings 128 and a second setof bearings 130. In this embodiment, the first set of bearings 128 islocated above the second set of bearings 130. The first and second setof bearings 128, 130 may be wheel bearings that are rotatably attachedto the moving element 104 around a shaft (not shown).

The first set of bearings 128 rides on the first guide rail 107. Thefirst set of bearings 128 has an edge profile that corresponds to theprofile of the first guide rail 107. In one embodiment, the first set ofbearings 128 has a “V” shaped profile that matches the opposite “V”shape profile of the first guide rail 107. The first set of bearings 128may alternately have a “U” shaped profile or another appropriatelyshaped profile intended to support the moving element 104 along thevertical axis. In some cases, the moving element 104 may have one ormore bearings for the first set of bearings 128.

The second set of bearings 130 rides on the second guide rail 109. Thesecond set of bearings 130 has an edge profile that corresponds to theprofile of the second guide rail 109. In an embodiment, the second setof bearings 130 has a flat profile (e.g., a flat wheel) that matches theflat profile of the second guide rail 109. The second set of bearings130 may be configured to roll a bit higher or lower on the second guiderail 109 to adapt to any non-parallelism with the first guide rail 107.In some cases, the second set of bearings 130 includes one or morebearings.

Higher precision is intended to be achieved over conventional conveyorsby supporting the moving element 104 with magnetic force and the firstset of bearings 128 to control the moving elements 104 along thevertical axis and the transverse axis of the track, including positionand rotation. In certain cases, the first set of bearings 128 preciselyconstrains the moving element 104 along the vertical axis and thetransverse axis of the track and precisely constrains pitch rotation andyaw rotation. The first set of bearings 128 provides precise movementand positioning along the longitudinal axis of the track with rollrotation about the longitudinal axis being constrains by the second setof bearings 130.

The second set of bearings 130 is intended to constrain rotation of themoving element 104 about the longitudinal axis of the track. In aparticular embodiment, the moving element 104 has two “V” shapedbearings 128 and two flat bearings 130. The two shaped bearings 128 andthe two flat bearings 130 (four bearings in total) are intended toprovide increased stability in rotation about the vertical axis or thelongitudinal axis of the track. This may allow for payloads mounted tothe moving element 104 that have higher cantilever moments than would beavailable with a three bearing configuration. With four bearings 128,130, the center of gravity of an added payload that is mounted to themoving element 104 may also be shifted farther away from the track 102.

FIG. 5 is a block diagram of an embodiment of a control architecture 201employed in the conveyor system 100. Zone controller 200 controls a zoneof the conveyor system 100 and the track 102 used in the zone of theconveyor system 100. A zone may include any number of coils. The coilsmay be grouped into ‘motors’. In a particular example, a motor mayinclude twenty interleaved coils. The motors may be equivalent in lengthto track sections 102; however this is not required as motors caninclude coils from more than one, or less than one, track section 102.The zone controller 200 may be used to interface with users of thesystem. The zone controller 200 is configured to monitor moving element104 positions and control the movement of moving elements 104 to go todesired destinations based on the moving element 104 position. As such,the zone controller 200 can be used for process (i.e.manufacturing-line) control. The zone controller 200 may also provide asupervisory diagnostic role by monitoring the track sections 102 (e.g.,by engaging in a continuous polling or pushing process) in order todetermine the current status of any track section 102 and whether anytrack section 102 has failed. It will be understood that, in some cases,the zone controller 200 may directly control each of the track sections102 or each of the motors.

The zone controller 200 may also be connected to other devices, such asprogrammable logic controllers (PLCs) (not shown) via input/output(I/O), network modules, software modules, Ethernet connections, or thelike. The PLCs may provide manufacturing-line station-processinginstructions to the zone controller 200, such as directing the nextdestination for a moving element 104 along the track 102, or providingstation-specific motion instructions in respect of a given movingelement 104.

As illustrated, the zone controller 200 is operatively connected to thestator armature 112 and coils 114 in the track sections 102 and controlsthe coils 114 in accordance with an independent trajectory or “move”command for each moving element 104 located therein.

The zone controller 200 is also operatively connected to the sensors 122situated in the track section 102. The zone controller 200 is used toimplement a closed-loop digital servo control system that controlsmovement of the moving element 104 by resolving the real-time positionof each moving element 104 located in the track section 102. When themachine readable medium 120 of a given moving element 104 moves over agiven sensor 122, moving element 104 position feedback is transmitted tothe zone controller 200. The zone controller 200 decodes the movingelement 104 position feedback to determine the position of the movingelement 104.

The zone controller 200 provides processing for sampling the sensors122, 123 and resolving the position of each moving element 104 locatedin the associated track section 102. Broadly speaking, the processingassociates the machine readable medium 120 of any given moving element104 with the identified sensors 122, 123 at any time so that a position,relative to the track section 102, of the given moving element 104 canbe calculated based on a fixed position of the associated sensor 122 or123 and a relative position of the machine readable medium 120 inrelation to the associated sensor 122 or 123. In addition, when themachine readable medium 120 simultaneously engages a plurality ofsensors 122, 123, the processing transfers or hands-off the associationor “ownership” of the moving element 104 from the current sensor 122 or123 to an adjacent engaged sensor 122 or 123. In this manner, theposition of an identified moving element 104 relative to the tracksection 102 can be continuously tracked.

Those skilled in the art will appreciate that the position sensingsystem may be magnetic, optical, color optical, capacitive, or may beanother alternative system. For example, the machine readable medium canbe a magnetic strip and the sensors 122, 123 can be correspondingmagnetic detectors. Such an embodiment may provide very fine resolution.In some cases the machine readable medium can be configured to provide 1micron or better resolution. The position accuracy of the moving element104 is only limited by the resolution of the position sensing system.

FIG. 6 illustrates another embodiment of control architecture 600 for alinear motor conveyor. In this embodiment, the control architecture 600includes a zone controller 602. The zone controller 602 may be connectedto other devices, such as programmable logic controllers (PLCs) 604 viainput/output (I/O), network modules, software modules, Ethernetconnections, or the like 606.

The zone controller 602 interfaces with and controls one or more motorgateways 608. In this example, as will be discussed, the motor gateway608 a is located on a left network 610 of motor gateways and motorgateway 608 b is located on a right network 612 of motor gateways. Eachnetwork 610, 612 may have the motor gateways 608 connected in series. Insome cases, each network 610, 612 may include two independentcommunication channels, a “command channel” and a “response channel”.The channels may have bidirectional or unidirectional data flow, and mayoperate independently of each other. The command channel may beresponsible for transmitting data from the zone controller 602 to themotor gateways 608, and the response channel may be responsible fortransmitting data from the motor gateways 608 to the zone controller602.

Each motor gateway 608 controls a number of coils grouped into a ‘motor’614 through power electronics circuits, in this case a coil driver 616.The coil drivers 616 contain circuitry that drives current to the coilsin the motor 614. The power electronics may also include thermistors(not shown) for temperature monitoring. The motor gateways 608 send coilcurrent set point data to the coil driver 616. The motor gateways 608also receive moving element 104 raw position data from the movingelement 104 position sensors 618 which may be passed along to the zonecontroller 602.

In some cases, the processing of the position, and the driving, of themoving element 104 will take place solely in the zone controller 602.The motor gateways 608 will relay only raw position sensor data to thezone controller 602. In addition, the motor gateways 608 will receivecoil current set points from the zone controller 602 to drive the coildriver 616. The processing of the input raw position data to allowoutput the coil current set points may be centralized in the zonecontroller 602. In some cases, the motor gateways 608 may have afeedback control structure to ensure the coils in the motor 614 do notsubstantially deviate from the coil current set point received from thezone controller 602.

Where there are curvilinear or curved track sections in a linear motorconveyor system, conventional systems are typically constrained. As theradius of the curved section is smaller towards the interior of thecurve than the exterior of the curve, conventional linear motor conveyorsystems typical encounter problems. In order to overcome this differencein radius, some conventional systems have coils that fan out towards theexterior of the curve, which may cause inconsistencies in magnetic flux.Other conventional systems may have each loop of the coil in the curvedsection at a different angle than the loops adjacent to it; which may bedifficult to construct and may require complex control systems to drivethe coils. As well, with coils that fan out or at different angles,there may be substantial difficulty in constructing and operatinginterleaved coils.

Conventional linear motor conveyor systems with curvilinear or curvedtrack sections may produce unwanted forces on a moving elementtraversing the curved track section. The excessive forces may be causedby undesirable rates of change of acceleration, hereinafter called a“jerk”. The jerk can have unwanted consequences of shifting componentsbeing carried by the moving element. The jerk may be especiallypronounced at the transition point between the curved section of trackand a straight section of track. Some conventional conveyor systems maylimit the speed of the moving elements as they travel through the curvedtrack section to minimize jerk. However, limiting speed may constrainconveyor system throughput. In some other conventional conveyor systems,the system configuration is limited such that certain stations orprocesses are only completed on straight sections of track prior to, orafter, moving elements travel through the curved sections of track.

Conventional linear motor conveyor systems also may have differentbearings/wheels of a moving element experience different forces orrotate at a different speed than other bearings/wheels of the movingelement. This effect may be especially pronounced where the movingelement travels on a top surface of a track. This effect may produceundesirable wear on the bearings/wheels and require that thebearings/wheels be made out of expensive material to resist wear, orrequire that expensive and complex differential systems be implementedon the moving element.

Conventional linear motor conveyor systems may have difficulty trackingmoving elements while the moving elements are traversing a curvilinearor curved section of track. Some conventional linear motor conveyorsystems use a different sensor system for curved track sections thanstraight track sections, which may add cost and complexity to theconveyor system.

Turning to FIGS. 7A, 7B and 7C, a top view of a powered curvilineartrack section 700, according to an embodiment, is shown. FIGS. 7B and 7Cillustrate an expanded view of section ‘A’ in FIG. 7A. The poweredcurvilinear track section 700 includes a curvilinear track portion 702,sometimes referred to as a curvilinear lamination portion because, insome embodiments, the track portion 700 is formed as a lamination ofseveral layers. FIG. 7A illustrates the curvilinear lamination portion702 as a single piece of lamination, but the curvilinear laminationportion 702 may be composed of multiple pieces of lamination attached toeach other. The curvilinear lamination portion 702 may be made of anymaterial that is structurally resilient and provides a suitable magneticpath; for example, a silicon steel or electrical steel such as AISI M19,or the like.

As best illustrated in FIGS. 7B and 7C, the curvilinear laminationportion 702 is provided with a plurality of slots 704 positioned aroundthe exterior of the curvilinear lamination portion 702. The slots 704may be grouped into a plurality of slot groupings 706. In the example ofFIGS. 7A to 7C, each slot grouping 706 may include eight slots 704;however, the slot groupings 706 can include any number of slots 704 tomatch the coil configuration in an accompanying motor unit 712 (whichwill be described below). The slots 704 in a slot grouping 706 may beapproximately parallel to one another. The slots 704 may be angledrelative to the curved edge of the curvilinear lamination portion 702.The slot groupings may come in pairs, as illustrated by a first slotgrouping 706 a (slot grouping 1) and a second slot grouping 706 b (slotgrouping 2) in FIGS. 7B and 7C. The pairs of slot groupings 706 will beapproximately parallel to allow the straight coils of the motor units712 to be inserted straight into the curvilinear lamination stack; asillustrated in FIG. 7C where motor unit 712 b is lined up for insertioninto slot grouping 1 706 a and slot grouping 2 706 b. The pair of slotgroupings 706 may be spaced such that there is one slot grouping 706intermediate the pair of slot groupings 706 to allow for interleavedmotor units, as described below. The slots 704 in a slot grouping 706may have different depths depending on the angle of the slot grouping706 relative to the curved edge of the curvilinear lamination portion702. The slots 704 can be any suitable depth as long as the motor unitcan be appropriately inserted in the slots 704, without being so deep asto materially affect the structural integrity of a lamination stack (asdescribed below). The slots 704 may have different depths withoutsubstantially affecting the control of the moving element 104 becausethe curvilinear lamination portion 702 is configured to provide a smoothmagnetic path as described herein.

The angle of the pair of slot groupings 706 may be determined, forexample, by: determining the midpoint between the pair of slot groupings706; determining the tangent to the curve of the exterior edge of thecurvilinear lamination portion 702 at that midpoint; determining theline perpendicular to the tangent; and determining the direction of theperpendicular line relative to the exterior edge of the curvilinearlamination portion 702. The direction of the perpendicular line is thedirection of all the slots 704 in the pair of slot groupings 706relative to the exterior edge of the curvilinear lamination portion 702.

In another example, the depths of the slots 704 can be determined bycutting the depths of the farthest-left slot 704 on the slot grouping 1706 a and the farthest-right slot on the slot grouping 2 706 b the samedepth as would be cut for a straight section 102 of track. The slots 704in between the farthest-left and farthest-right slots 704 are cut deeperto allow the motor unit 712 to be inserted straight in, where theinnermost slots 704 may be cut with the deepest depth due to thecurvilinear profile of the track section 700.

Turning to FIG. 8, a perspective view of the powered curvilinear tracksection 700 is shown. The powered curvilinear track section 700 is shownas a curvilinear lamination stack 708. The curvilinear lamination stack708 is a stack of curvilinear lamination portions 702 which are lined upand mounted one on top of each other until a predetermined stack height710 is reached. The curvilinear lamination portions 702 are attached toeach other to form the curvilinear lamination stack 708 using a suitableglue, epoxy, or the like. The predetermined stack height 710 is selectedto be greater, or approximately match, the height of the motor units712, such that the motor units 712 can be inserted into the curvilinearlamination stack 708, as will be described. A lamination stack may bebeneficial in reducing eddy currents that can result in energy lossesand increased heat in the motor. However, in some embodiments, the tracksection 700 may be formed using a monolithic motor core made out of asolid ferromagnetic metal like iron, or the like, or a ferromagneticcompound.

Turning to FIGS. 9A and 9B, a perspective view and top view,respectively, of the powered curvilinear track section 700 is shown. Thecurvilinear lamination stack 708 is shown with pairs of motor units 712inserted into to the slots 704, except for one motor unit 712 pair whichare not shown as inserted into the slots 704 for illustration purposes.

In one embodiment, the pair of motor units 712 comprises two types ofmotor units 712: an inner motor unit 712 a and an outer motor unit 712b. The motor unit 712 includes an armature 716 having a top 718, abottom 720, a first side 722, and a second side 724. The motor unit 712also has a central rectangular spacing 726. The spacing 726 may have awidth that is slightly larger than the width of a side 722 or 724 of themotor unit 712 in order to allow interleaving of motor units 712 (aswill be described); for example, the spacing 726 width may be 25 mm.Along the armature 716 are a plurality of motor coils 714 grouped intowindings. The motor coils 714 may be made of, for example, copper,aluminum, or the like. In this example, there are eight windings;however, any suitable amount of windings may be used as long as thewindings configuration matches the slot grouping 706 configuration. Thewindings of the motor coils 714 at the first side 722 and second side724 may be wound to be approximately straight and vertical. The windingsof the motor coils 714 at the first side 722 are approximately parallelwith the windings of the motor coils 714 at the second side 724. In afurther example, the windings of the motor coils 714 may be etchedwindings in a multi-layer circuit board. In some instances, a motor coil714 may refer to a motor unit 712.

The motor coils 714 a of the inner motor unit 712 a are inserted intothe slots 704 of the curvilinear lamination stack 708. The motor coils714 a on each side 722 a, or 724 a of the inner motor unit 712 a arelined up and inserted into an associated slot grouping 706. The innermotor unit 712 a is configured such that there is one slot grouping 706in between the sides 722, 724 of the inner motor unit 712 a. The motorcoils 714 b of the outer motor unit 712 b are inserted into the slots704 of the curvilinear lamination stack 708 in an overlappingrelationship with the inner motor unit 712 a. Thus, the motor coils 714of the pair of motor units 712 are interleaved. In order to overlap themotor units 712, the motor coils 714 b on one side 722 b or 724 b of theouter motor unit 712 b are lined up and inserted into the slot grouping706 located between the sides of the inner motor unit 712 a. At the sametime, the motor coils 714 b on the other side 722 b or 724 b of theouter motor unit 712 b are lined up and inserted into the slot grouping706 located outside one of the sides 722 a, 724 a of the inner motorunit 712 a; in this case, lined up and inserted into the slot grouping706 to the left of the inner motor unit 712 a. Inner motor units 712 aand outer motor units 712 b are inserted in this way along the length ofthe powered curvilinear track section 700.

The motor units 712 may be joined to the curvilinear lamination stack708 using any suitable means known in the art; for example: inserting aninsulator prior to insertion of the motor unit 712, inserting the motorunit 712, and then providing an adhesive over the motor unit 712. Theadhesive may be, for example, an epoxy potting compound.

The top 718 a and bottom 720 a of the inner motor unit 712 a, and insome cases the top 718 b and bottom 720 b of the outer motor unit 712 b,may be curved in order to have the center of balance of the inner motorunit 712 a and the outer motor unit 712 b biased towards the curvilinearlamination stack 708. In other cases, only the top 718 a and bottom 720a of the inner motor unit 712 a may be curved. The top 718 a and bottom720 a of the inner motor unit 712 a may have a more acute angle than theouter motor unit 712 b to ensure that motor coils 714 of both motorunits 712 can be fully inserted into the slots 704. As the inner motorunits 712 a overlap the outer motor units 712 b for an interleavedarrangement, only two types of motor units 712 may be required. It isintended that this may provide an advantage over conventional systemswhich typically require a curved section to have a number of differentmotor unit shapes to match conventional coil arrangements that fan outor at different angles to each other. Having only two types of motorunits 712 is intended to have less complexity, increased flexibility andless cost.

In other embodiments, the truck section may use only one type of motorunit. In this case, motor units may be inserted into slots in a mannersuch that the motor units are adjacent to each other and are notinterleaved but the slot groupings may be cut at predetermined angles toproduce results as described herein.

As described, the slots 704 of a slot grouping 706 may be approximatelyparallel. As such, the approximately vertical motor coils 714 can beinserted straight in without further configuration required. As such,the motor units 712 may be used for both powered curvilinear tracksections 700 and powered linear track sections 102. The dual usage ofthe motor units 712 can increase flexibility of the system and reducecost and complexity.

As described above, slots 704 may be angled relative to the curved edgeof the curvilinear lamination portion 702. This angle may be configuredto be appropriate for the inserted motor coil 714 at that particularlocation of the curvilinear lamination portion 702. The angle isintended to be optimized to the curve profile of the curvilinearlamination portion 702 such that the powered curvilinear track section700 can have consistent, smooth, efficient and/or powerful control of amoving element 104 while it is traversing the powered curvilinear tracksection 700.

The embedded coils 714 of the motor units 712 can be individuallyexcited by the coil driver 616 so that an electrically-induced magneticflux produced by the motor unit 712 is located adjacent to a givenmoving element 104 to be controlled, in a direction normal thereto,without affecting adjacent moving elements 104. The motive force fortranslating each moving element 104 arises from the MMF force producedby each moving element 104 and the stator armature 716, i.e., by thetendency of the corresponding magnetic fluxes provided by the statorarmature 716 and moving element 104 to align. A zone controller 602enables separate and independent moving MMFs to be produced along thelength of the powered curvilinear track section 700 for each movingelement 104 so that each moving element 104 can be individuallycontrolled with a trajectory profile that is generally independent ofany other moving element 104. Structurally, like the straight tracksection 102 described above, the powered curvilinear track section 700may thus be broadly classified as a moving-magnet type linear brushlessmotor having multiple moving elements 104.

In conventional linear motor conveyor systems with curved tracksections, curved track sections may produce unwanted forces on a movingelement traversing the curved track section. The excessive forces may becaused by undesirable rates of change of acceleration, hereinaftercalled “jerk”. The jerk can have unwanted consequences of shiftingcomponents being carried by the moving element. The jerk may beespecially pronounced at the transition point between the curvilineartrack section 700 and straight section 102 of track. In conventionallinear motor conveyor systems with curved track sections, a movingelement traversing the curved track section may reach a speed where thecentrifugal force exceeds the holding force of the permanent magnets andcauses the moving element to dislodge from the track.

Further, in conventional linear motor conveyor systems, sudden changesin a magnet gap, such as the transition point between two tracksections, can result in “magnetic bumps” to a moving element.Conventional conveyor systems typically have difficulty maintainingsmooth motion across regions with magnetic bumps, which may undesirablybump and shift components being transported by the moving element.Conventional conveyor systems may also have difficultly stopping andholding a moving element in the region of a magnetic bump. Further, whenthe conveyor system is powered off and closed loop control stops, amoving element straddling a magnet bump could have undesired movementdue to residual magnetic forces from the permanent magnets of theconventional conveyor system.

It is an intended advantage of the present disclosure to have a trackprofile for a curvilinear section of track that minimizes jerk andallows high speeds through the curve without the centrifugal forcebecoming problematic. It is also an intended advantage to minimize theimpact of magnetic gap changes that may occur as the moving element 104traverses curvilinear sections of track 1000. It is a further intendedadvantage to minimize the impact of magnetic gap changes at thetransition areas between straight and curvilinear sections of track.

As shown in the embodiment of FIGS. 10A and 10B, a curvilinear tracksection 1000 may be configured with a profile of curvature intended tominimize jerk on the moving element 104 as it traverses through thecurvilinear track section 1000. In some cases, the jerk may also beminimized when the moving element 104 transitions from straight tracksections (not shown) to the curvilinear track sections 1000, and fromthe curvilinear track sections 1000 back to the straight sections.

In some embodiments, the physical track profile may be configured suchthat the moving element 104 will have a rate of change of angularvelocity which is sinusoidal over the span of the curvilinear tracksection 1000. FIG. 10A illustrates an example of a top view of acurvilinear track 1000 with a sinusoidal angular velocity track profile.With a sinusoidal angular velocity track profile, a moving element 104travelling at constant velocity would travel through the 180 degreecurvilinear track section 1000 with a sinusoidal rate of change ofangular velocity.

To minimize unwanted forces, any change in direction of travel of themoving element 104, that is, its angular velocity, should be gradual. Aswell, any change in the magnetic coupling between the curvilinear tracksection 1000 and the moving element 104 should be gradual to minimizeunwanted forces, such as “magnetic bumps”. A sinusoidal angular velocitytrack profile has been found to minimize unwanted forces, such as thosecaused by jerk and magnetic bump, as the moving element 104 traversesthe curvilinear track section 1000.

A sinusoidal angular velocity track profile may be configured to handlea moving element 104 going from an angular velocity of approximatelyzero at the entry to the curvilinear track section 1000, up to a peakvalue of angular velocity at the apex of the curvilinear track section1000, and back down to approximately zero as moving element 104 exitsthe curvilinear track section 1000. Transitioning this from an initialvalue of approximately zero to some peak value and then back toapproximately zero in a sinusoidal fashion, in some cases akin to simpleharmonic motion, is intended to minimize the above unwanted forces.

Further, the sinusoidal angular velocity track profile may also allowmoving elements to traverse the curvilinear track section at relativelyhigh speeds, and carrying relatively heavy components, without exceedingthe holding force of the magnets of the moving element 104 and causingthe moving element 104 to dislodge from the curvilinear track section1000. In the example of FIG. 10, the sinusoidal angular velocity trackprofile is applied to a 180° curvilinear track section; however, thesinusoidal angular velocity track profile may be applied to anycurvature of track, for example, 30°, 45°, 90°, or the like. Thesinusoidal angular velocity track profile may also be applied to inside(concave) curves, curves in three-dimensions, or the like.

In some cases, to further minimize unwanted forces, such as those causedby jerk, a transition curve may be used to join a straight track sectionto a curvilinear track sections such as, for example, a track section ofconstant radius. A transition curve may also be used to join acurvilinear track section to a straight track section.

FIG. 11 illustrates a top view of a curvilinear track section 1000 witha transition curve. In this case, the curvilinear track section 1000 hasa clothoid profile region 1010 at or near the ends of the curvilineartrack section 1000. The curvilinear track section 1000 also has aconstant curvilinear region 1012 with a constant radius between theclothoid profile regions 1010. In still other cases, the constantcurvilinear region 1012 may have another appropriate profile, includinga clothoid profile. In some cases, the curvilinear track section 1000may include a linear portion 1014 at the ends of the curvilinear tracksection 1000, as will be described. The example of FIG. 11 illustrates acurvilinear track section 1000 with a 180° curve; however any suitablecurve angle for example, 30°, 45°, 90°, or the like, may be used. Inthis example, the constant curvilinear region 1012 has an angle ofapproximately 147° and the clothoid transition regions 1010 on bothsides of the constant curvilinear region 1012 has an angle ofapproximately 16.5°. The three regions thus add up to 180°, the totalangle of the curvilinear track section 1000. The size of the clothoidtransition regions 1010 is configurable and the two transition regionsdo not necessarily have to be the same length or angle. The clothoidtransition regions 1010 may be applied to any curvature of track, forexample, 30°, 45°, 90°, or the like. The clothoid transition regions1010 may also be applied to inside (concave) curves, curves inthree-dimensions, or the like.

A curvilinear track section 1000 with clothoid transition regions 1010may also reduce jerk on a moving element 104 as it travels through theregion of the curvilinear track section 1000 where there is a constantcurvilinear region 1012. As well, it is an intended advantage that aconveyor station can work on components carried by a moving element 104without undue constraint if the moving element 104 is in a region ofconstant radius 1012.

In some cases, the curvilinear track section 1000 may have a linearportion 1014 in the region where the clothoid transition regions 1010joins with a straight track section (not shown). The linear portion 1014is intended to ease the transition into the curve and accommodate properguide rail alignment on entering the curve.

In other cases, a wider turn may be desirable. In this case, a smallstraight track section may be included generally at the apex of theturn. The small straight section may be useful to, for example, provideor allow for teach points and make programmable adjustments at a stationalong a straight line or for other purposes.

As a linear motor conveyor may comprise separate track sections ormodules, adjacent track sections may need to be accurately aligned suchthat moving elements can travel smoothly across track sectionboundaries. Alignment procedures are generally known in the art and mayinclude the use of, for example, gauges, dial indicators, rulers, or thelike. When a straight track section is joined with a curvilinear tracksection 1000, alignment may be difficult if the curvature of thecurvilinear track section 1000 starts immediately. This difficulty maybe due to, for example, the difficultly encountered when attempting touse gauges, dial indicators and the like on a curvilinear track. Thus, alinear portion 1014 prior to curvilinear regions of the curvilineartrack section 1000 may allow for proper and easy alignment of thecurvilinear track section 1000 with other track sections. In the exampleof FIG. 11, the curvilinear track section 1000 has an 18 mm linearportion 1014 on both ends of the curvilinear track section 1000;however, any suitable length may be used for the linear portion 1014.This relatively small linear portion 1014 accommodates alignment of theguide rails, as aligning two straight guide rails may be morestraightforward than attempting to align one straight guide rail and onecurved guide rail. The linear portion 1014 may be fabricated into thelamination stack.

As a linear motor conveyor system 100 may comprise separate tracksections or modules, adjacent track sections may need to be accuratelyaligned such that moving elements 104 can travel smoothly across tracksection boundaries. If the surfaces of the track sections are notaccurately aligned at the section boundaries, the bearings 128, 130 ofthe moving element 104 may not have a smooth transition when travellingacross these boundaries. A misaligned transition may cause wear,vibration, audible noise, or the like. In an example, a linear motorconveyor system 100 having the track sections 102 illustrated in FIG. 1may require accurately aligning the first guide rail 107 withinapproximately +/−20 microns for smooth, precise motion across tracksection 102 joints.

Conventionally, problems may occur when attempting to accurately alignthe rails (or riding surfaces) of the adjacent track sections due tomachining stack up tolerances. Multiple stack up tolerances may bepresent in each track section that may influence the location of thesurfaces of the track section. Once guide rails or surfaces of twoadjacent track sections are accurately aligned using procedures known inthe art, the track sections need to be structurally bound together towithstand the forces applied to the track sections. Conventionalconveyor systems may have difficulties structurally binding two adjacentsections together, while maintaining accurate alignment of the surfacesof the track sections. Conventional conveyor systems typically requireexpensive and/or complex mechanisms.

Turning to FIGS. 12A and 12B, a top view of two adjacent straight tracksections 102 joined using a wedge aligner 1200, according to anembodiment, is shown. The wedge aligner 1200 includes a casing 1202, afixed mount 1204, a wedge 1206, an adjuster 1208 and fasteners 1210. Thefixed mount 1204 may be rigidly attached to one of the adjacent tracksections 102, the right track section 102 in the example of FIG. 12,using the fasteners 1210. The fixed mount 1204 is flexibly attached tothe other adjacent track section 102 using the fasteners 1210. A wedge1206 is positioned intermediate the fixed mount 1200 and the otheradjacent track section 102. In the example of FIG. 12, the wedge 1206 isa 7° inclined plane; however, any suitable angle or shape may be used.

The wedge 1206 may be translated back and forth along the longitudinalaxis of the straight track sections 102 using the adjuster 1208. In theexample of FIG. 12, the adjuster 1208 is an adjustable screw; however,any suitable mechanism for translating the wedge 1206 back and forth iscontemplated. The wedge 1206 may define holes through its face (notshown) for permitting passageway of the fastener 1210. The holes may beshaped such that translation of the wedge 1206 back and forth does notresult in the sides of the holes abutting the fastener 1210.

In order to align the two adjacent track sections 102, the guide rails107, 109 may be accurately aligned with procedures known in the art. Thewedge 1206 may then be inserted between the fixed mount 1204 and thetrack section 102 to compensate for stack up tolerances. The wedge 1206is adjusted using the adjuster 1208 to ensure the wedge 1206 is firmlyin place. The fasteners 1210 may then be tightened to rigidly bind thetwo adjacent track sections 102 together. Even after tightening, thewedge 1206 stays in place to compensate for machining tolerances. Whenthe wedge aligner 1200 is tightened, the guide rails 107, 109 willmaintain an accurate alignment due to the fact the wedge 1206 has beenfirmly inserted to compensate for the stack up tolerances. In furthercases, the adjuster 1208 may also be used as an adjustment tool for finealignment of the surfaces of the track sections 102. In an example, theadjuster 1208 may provide fine adjustment of approximately +/−20 micronsprior to tightening of the fasteners 1210 in the final, accuratelyaligned location. In some cases, the wedge aligner 1200 has a casing1202 around at least a portion of the exterior of the wedge aligner 1200in order to protect the components of the wedge aligner 1200. Preciseadjustments for alignment may be particularly important where there areshaped guide rails on the track sections.

FIGS. 13A and 13B illustrate a top view of a wedge aligner 1300according to another embodiment. In the embodiment of FIG. 13, the wedgealigner 1300 joins a straight track section 102 and a curvilinear tracksection 1000. In this embodiment, the wedge aligner 1300 also includes acasing 1302, a fixed mount 1304, a wedge 1306, an adjuster 1308 andfasteners 1310. In this embodiment, the fixed mount 1304 may have anangle to both rigidly attach to one of the track section, in this casethe curvilinear track section 1000, and flexibly attach to the othertrack section, in this case the straight track section 102. In theexample of FIG. 13, the flexible mount 1304 has an angle ofapproximately 90°; however, any suitable angle may be used to attach tothe adjacent track sections. Otherwise, the wedge aligner 1300 operatesin the same manner as the wedge aligner 1200 in the embodiment of FIG.12.

Conventional linear motor conveyors with curved track sections typicallyencounter problems where wheels or bearings on a moving element rolldifferently on the curved section of track than they do on a straightsection of track. In some conventional conveyor systems, the wheels orbearings may skid on the curved section of track, which may result inwear and/or require expensive anti-skid or wear resistant materials. Insome other conventional conveyor systems, further mechanical elementsmay be required in order to have moving elements operate on bothstraight and curved sections of track. Further, conveyor systemperformance may be constrained (i.e. speed, acceleration or the like) onthe curved sections of track if the wheels or bearings of the movingelement have to operate differently on the curved sections of track.

Turning again to FIGS. 10A and 10B, the curvilinear track section 1000and the bearings 128, 130 of the moving element 104 may be configured toreduce wear and deterioration of the bearings 128, 130. Similar to thestraight track section 102, the curvilinear track section 1000 mayinclude two guide rails: a first guide rail 1002 which may be located onthe top of the exterior side of the curvilinear track section 1000; anda second guide rail 1004 which may be located on the bottom of theexterior side of the curvilinear track section 1000. Both the firstguide rail 1002 and the second guide rail 1004 may be located to the topof and to the bottom of, respectively, the motor units 1006. In somecases, the first guide rail 1004 may have a “V” or “U” shaped profile tosupport and guide the moving element 104, and the second guide rail 1004may be a smooth surface with a flat profile. The vertex of the firstguide rail 1002 and the surface of the second guide rail 1004 areapproximately aligned to be co-planar. As well, the vertex of the firstguide rail 1002 and the surface of the second guide rail 1004 areconfigured to have approximately the same profile of curvature.

The moving element 104, illustrated in FIGS. 4A and 4B, includesbearings 128, 130 that have approximately the same radius; whereby theradius for the first set of bearings 128 is measured from the shaft ofthe bearings 128 to the portion of the bearings 128 that abuts thesurface of the second guide rail 1004; and the radius of the second setof bearings 130 is measured from the shaft of the bearings 130 to theportion of the bearings 130 that abuts the vertex of the first guiderail 1002. The space between the shafts of the first set of bearings 128and the space between shafts of the second set of bearings 130 may beapproximately equal.

As the moving element 104 travels along the side of both linear andcurvilinear track sections, the bearing 128 or 130 configuration of themoving element 104 in conjunction with the guide rail 1002, 1004configuration of the curvilinear track section 1000 is intended to allowthe bearings 128, 130 to maintain approximately full contact with theguide rails 1002, 1004 throughout the moving element's 104 traversal ofthe curvilinear track section 1000. As all the bearings 128, 130 of themoving element 104 are approximately in the same contact with the guiderails 1002, 1004, a horizontal shelf 117 attached to the moving element104 can stay approximately level as the moving element 104 traverses thecurvilinear track section 1000. Further, the bearings 128, 130 of themoving element 104 rotate and maintain contact in the same manner on thecurvilinear track section 1000 as the bearings 128, 130 do on thestraight track sections 102, allowing a smooth transition andconsistency as the moving element transitions from straight tracksection 102 to curvilinear track sections 1000. Conventional linearmotor conveyor systems typically have some bearings/wheels on a movingelement travel farther than other bearings/wheels of the moving elementwhile the moving element is traversing a curved section. In contrast,the current embodiments may have diminished skidding, wear or the likeon the bearings 128, 130. As such, the bearings 128, 130 may last longerand/or can be made of less expensive materials.

As shown in the embodiment of FIGS. 10A and 10B, a curvilinear tracksection 1000, like the straight track sections 102, may have sensors1008 positioned along the top surface of the curvilinear track section1000. The sensors 1008 may be offset such that there are inner sensors1008 a and outer sensors 1008 b. It is an intended advantage that thesame sensors 1008, 122, 123 can be used for both the curvilinear tracksections 1000 and the straight track sections 102; allowing sensors1008, 122, 123 to read the same machine readable medium 120 mounted onthe extension 118 of the moving elements 104. It is also an intendedadvantage that a high-resolution machine readable medium 120 may be usedon the curvilinear track sections 1000 with approximately similarperformance (for example, resolution and speed) as on the straight tracksections 102. Further, it is an intended advantage that a machinereadable medium 120, in the form of a linear strip, can be used on boththe curvilinear track sections 1000 and the straight track sections 102.

The sensors 1008 are positioned on the curvilinear track section 1000such that the sensors 1008 are oriented perpendicular to the directionof motion. In this orientation, a linear strip machine readable medium120 can be used on both straight sections of track 102 and curvilinearsections of track 1000. The linear strip machine readable medium 120will change angle as the moving element 104 traverses the curvilineartrack section 1000. The sensors 1008 are configured to handle thisangular variation and are able to provide useable position information.In other cases, the sensors 1008 may have a design that is sufficientlytolerant of the angular variation. The linear strip machine readablemedium 120 may be configured to have a width that passes over thesensors at all points in the curvilinear track section 1000, and assuch, the system may be able to receive valid position readings from thesensors 1008 at any position on the curvilinear track section 1000.

FIG. 10A illustrates the variable spacing of the sensors 1008 with amoving element 104 on the curvilinear track section 1000. The variablespacing of the sensors 1008 are positioned such that there is sensoradequate for engagement with the linear strip machine readable medium120 as the moving element 104 traverses the curvilinear track section1000. The length and width of the extension 118, in conjunction with thepositioning of the sensors 1008, may be configured such that theextension 118 overlaps at least two sensors 1008 at any given time. Thisconfiguration may allow adequate sensor engagement with the linear stripmachine readable medium 120 at any given time. In other cases, thelength and width of the extension 118, in conjunction with thepositioning of the sensors 1008, may be configured such that there isadequate overlap of two sensors 1008 for handoff from one sensor 1008 tothe other sensor 1008.

Straight track sections 102 may have a common linear frame of referenceto use for calibration. In an example, if two sensors 1008 are expectedto be 62.500 mm apart but the actual data received expresses that theyare 62.550 mm apart, the system may apply a calibration offset of 0.050mm to compensate for actual system tolerances. However, this calibrationprocedure may not hold true for curvilinear track sections because theraw data from any two sensors 1008 are not in the same linear frame ofreference. Particularly, the calibration data may be off due to: thedepth of the curvilinear track section 1000, the sensors 1008 being on adifferent curve angle than the path of the moving element 104 whichfollows the guide rails 1002, 1004; the linear strip machine readablemedium 120 on the moving element 104 may change angle as the movingelement 104 traverses the curvilinear track section 1000, which may givenon-linear readings; and/or certain manufacturing tolerances may occurin two dimensions.

For curved track section, in some cases, it may be a problem tocalibrate one of the sensors to a known absolute zero, which may be usedas a reference to calibrate the other sensors. Accordingly, the firstsensor 1008 on the curvilinear track section 1000 may be calibrated tothe last sensor 122 or 123 on the straight track section 102; as thesensors 122 or 123 on the straight track section 102 have a knownabsolute value once calibrated. If the curvilinear track section 1000has a linear portion 1014, the first sensor 1008 in the curvilinearregions 1010, 1012 can be calibrated to the last sensor in the linearportion 1014 as the sensors 1008 in the linear portion 1014 have a knownlinear frame of reference.

In an example, when a moving element 104 traverses the curvilinear tracksection 1000, the linear strip machine readable medium 120 may beconfigured to have a length such that there is always an overlap regionwhen handing off from one sensor 1008 to the next sensor 1008. While thelinear strip machine readable medium 120 is in this overlap region, acommon variable is the velocity of the moving element 104, which may bedetermined by the rate of change of the sensor 1008 readings. As well,while the linear strip machine readable medium 120 is in this overlapregion, the zone controller 200 is getting readings from two sensors1008 from the same moving element 104 at the same time. The movingelement 104 velocity from these two readings must necessarily be thesame as both readings measure the same physical moving element 104. Assuch, an estimate may be made of the true velocity of the moving element104. The true velocity measurement may then be used to build acorrelation between actual moving element 104 travel versus what isbeing reported by the sensors. In an example, if one calibrated sensor,such as a sensor 122 or 123 from the linear track section 102, indicatesthe moving element 104 is moving at 0.200 m/sec, a predeterminedposition table may be used for the second sensor 1008, from thecurvilinear track section 1000, such that the readings coming from thesecond sensor 1008 are adjusted to match the 0.200 m/sec. Sensor 1008calibration, based on matching velocity, can then be performed on eachsensor 1008 around the curvilinear track section 1000.

Any sensor 1008 will typically read reasonably “true” when the movingelement 104 is nearly centered on the sensor 1008, because, at thispoint, the machine readable medium's 120 angle of travel is nearlyaligned to the sensor 1008. This fact may be useful when analyzing theoutput of multiple sensors, to produce a reasonable estimate of positionand/or velocity. Velocity may be used because, although the designedlocations of the sensors 1008 may be known, the actual physical locationof the sensors 1008 may not be precisely known due to manufacturingtolerances, which has the possibility of introducing errors. The sensors1008 are used to estimate the velocity of the moving element 104.

There may also be two mechanisms for reducing noise in the measurementsof velocity: attaching some mass to the moving element 104, which maygive the moving element 104 some physical inertia and which may help themoving element 104 retain a constant velocity; and applying an optimizeddigital filter to the measured values.

The position table may be used to “linearize” the output from sensors1008 on a curvilinear section of track 1000. A position table may bedefined for each sensor 1008. Each position table may consist of anordered set of value pairs (r, p), where “r” is the reading provided bythe sensor, and “p” is the moving element's 104 actual position alongthe rail, relative to the location of the sensor 1008. The range ofvalues in each table is defined such that it covers the entire usablerange of travel, in which the machine readable medium 120 can be read bythe sensor 1008. The moving element's 104 position along the guide rail1002 or 1004 of the curvilinear track section 1000, relative to thesensor 1008, can be calculated by simple interpolation within theposition table. The moving element's 104 absolute position on thecurvilinear track section 1000 may then be determined by adding thecalibrated location of the sensor 1008.

As the curvilinear track section 1000 may not have a common linear frameof reference, the sensors 1008 may be on a different curve angle thanthe guide rails. As such, the linear strip machine readable medium 120on the moving element 104 may change angles as the moving element 104traverses the curvilinear track section 1000; which may give non-linearreadings and certain manufacturing tolerances may occur in twodimensions. Accordingly, the raw encoder values may be resolved tolinear units of measure, such as, for example, linear microns.

The sensors 1008 produce a value that indicates a distance along themachine readable medium 120. Due to the curvature of the curvilineartrack section 1000, the translation between the distance read by thesensor 1008 and the “distance along the rail” traversed by the movingelement 104 is non-trivial. The values in the position tables are usedto resolve the position of the moving element 104 by performing aposition table lookup followed by linear interpolation between twoadjacent points in the table.

In some cases, the position table may be used to translate a series ofzone boundaries on a linear strip machine readable medium 120 to acorresponding linear distance along the curvilinear track section 1000.A linear approximation may then be made to the raw data received whilethe linear strip machine readable medium 120 is within the zoneboundary. The approximation may then be translated, via the positiontable, to linear measurements of the moving element 104 along thecurvilinear track section 1000.

In a particular example, a linear strip machine readable medium 120 maybe divided into a number of zones. The zones may be 4 mm wide, and witha 144 mm linear strip machine readable medium 120, there may be up to 36zones. In some cases, there may be less usable zones for tighterportions of the curvilinear track section 1000. A theoretical positiontable is generated for each of the 4 mm zone boundaries; in thisexample, there are 36 numbers in the position table. The position tabletranslates the 36 zone boundaries to a corresponding linear measurementin microns. In this example, the values in the position table define howfar the center of the moving element 104 would have travelled along thesurface of the second guide rail 1004 on the curvilinear track section1000. As such, the position table translates 4 mm zone crossings todistance travelled along the curve in microns. In some cases, thetheoretical position table may be generated virtually, for example,using 3D CAD simulation software. In the simulation, a moving element104 may be placed at the area where the linear strip machine readablemedium 120 is approximately on a boundary of a given 4 mm zone withinthe linear strip machine readable medium 120. A determination is thenmade regarding how far the center of the moving element 104 has totravel along the surface of the second guide rail 1004. A valuerepresenting this linear position of the pallet on the curvilinear tracksection 1000 can be approximated. Any suitable approximation may beused; for example, a linear approximation, a best fit curve, moredensely spaced data points, or the like. This measurement may berepeated for each of the 36 zone boundaries for each sensor. With allthe measurements, a theoretical position table may be generated for eachsensor on the curvilinear track section 1000. In a further case, thevirtual simulation may be conducted as a physical experiment. As theposition table may be theoretical, there may be tolerance variation withthe actual curvilinear track section 1000. The above calibrationprocedure, based on matching velocity, can then be used to provide moreaccurate approximation for the values in the position table. After whichthe zone boundaries may be accurately translated to distance travelledalong the curve.

It is an intended advantage that the moving element 104 positions areconsistent on both straight sections of track 102 and curvilinearsections of track 1000. In an example, if a curvilinear section 1000 anda straight section 102 are both 1000.000 mm long, the resolved positionof a moving element 104 along either type of track section may appearthe same for teaching, programming and configuration of the linear motorconveyor system 100. The non-linear position information is resolvedfrom the sensors 1008 on the curvilinear sections of track 1000 to thecenter of the moving element 104 along the second guide rail 1004 (orthe vertex of the first guide rail 1002). As center of the movingelement 104 is used to resolve position information on the straightsections 102 of track, resolving it to this area may allow the positionsto be consistent for both straight sections of track 102 and curvilinearsections of track 1000. In other cases, the position information may beresolved from the sensors 1008 on the curvilinear sections of track 1000to the center of the moving element 104 along the face of the motor unit712. Any appropriate reference frame on the moving element may be used;for example, the left or right side of the moving element, or the like.Further, any appropriate reference frame along the curvilinear tracksection 1000 may be used; for example, the vertex or base of the firstguide rail 1002, the face of the motor unit 714, or the like. The pointsof reference for the readings and measurements may be adjusted asneeded.

The curvilinear track section 1000 may have an additional gain or‘boost’ applied to the output of the control loop to either increase ordecrease coil currents; such as for adapting to variations in magneticcoupling through the curvilinear track section 1000. In a certain case,an increase in magnetic gap may form as the moving element 104 traversesthrough the curvilinear track section 1000. The magnetic gap may be thedistance between the magnets of the moving element 104 and thecurvilinear track section 1000. The magnetic gap may increase as themoving element 104 traverses through the curvilinear track section 1000until the magnetic gap may be at its greatest at the apex of the curve.Correspondingly, the magnetic coupling of the moving element 104 to thecurvilinear lamination stack 708 may be at the lowest level at the apexof the curvilinear track section 1000. The magnetic gap is generallyrelated to the radius of the curvilinear track section 100. For acurvature with continuously varying radius, the magnetic gap may alsovary continuously. Due to the magnetic gap increase, a boost in currentto the motor coil 714, resulting in more thrust on the moving element104, may be applied as the moving element 104 approaches and traversesthrough the apex of the curvilinear track section 1000. In some cases,the boost may be a trapezoidal boost that may start at a scale factor ofunity gain as the moving element 104 enters the curvilinear tracksection 1000. The boost may increase as the moving element 104 traversesthe curvilinear track section 1000 such that the boost may reach a scalefactor of approximately two when the moving element 104 reaches the apexof the curvilinear track section 1000. The boost may then decrease suchthat the boost again reaches a scale factor of unity gain as the movingelement 104 leaves the curvilinear track section 1000. Any suitablescale factors for the boost may be used such that the magnetic gapbetween the moving element 104 and the lamination stack is suitablyreduced.

FIG. 14 illustrates a flowchart for a method 1400 of manufacturing apowered curvilinear track section 700, according to an embodiment. At1402, a curvilinear lamination portion 702 is formed into a suitableshape. In the example of FIG. 7, the curvilinear lamination portion 702has a ‘U’ shape such that it forms an 180° turn. In some cases, thecurvilinear lamination portion 702 may be formed out of multiple piecesof lamination. In further cases, the shape of the curvilinear laminationportion 702 may have a sinusoidal angular velocity track profile. Inother cases, the shape of the curvilinear lamination portion 702 mayhave at least one region with clothoid profile 1010 and a region withconstant radius 1012. In yet other cases, the curvilinear laminationportion 702 may have a linear portion 1014 at the ends of thecurvilinear lamination portion 702. In this case, the curvilinearlamination portion 702 has a 180° turn; however, the turn may be, forexample, 45°, 90°, or the like. The shape of the curvilinear laminationportion 702 can also form inside (concave) curves, curves inthree-dimensions, or the like.

At 1404, slot grouping 1 706 a is cut out of the exterior edge of thecurvilinear lamination portion 702. The slots may be cut out using asuitable means; for example, stamped, laser cut, water jet cut or thelike. In the example of FIG. 7, a slot grouping 706 consists of eightslots 704; however, a slot grouping can consist of any suitable numberof slots. The slots 704 have a predetermined angle relative to theexterior edge of the curvilinear lamination portion 702. All the slots704 of a slot grouping 706 share the same angle. Each slot 704 in theslot grouping 1 706 a may have a different depth. The depth will dependon the angle of the slot relative to the exterior edge of thecurvilinear lamination portion 702 as the slots 704 need to havesufficient depth such that the motor unit 712 can be partially or fullyinserted into the slots 704. In an example, the depths of the slots 704can be determined by: cutting the depths of the farthest-left slot 704on the slot grouping 1 706 a and the farthest-right slot on the slotgrouping 2 706 b the same depth as would be cut for a straight section102 of track; and the slots 704 in between the farthest-left andfarthest-right slots 704 are cut deeper to allow the motor unit 712 tobe inserted straight, where the innermost slots 704 may be cut with thedeepest depth due to the curvilinear profile of the track section 700.

At 1406, slot grouping 2 706 b is cut out of the exterior edge of thecurvilinear lamination portion 702. The slots 704 of slot grouping 2 706b share the same predetermined angle relative to the exterior edge ofthe curvilinear lamination portion 702 as slot grouping 1 706 a.Similarly, each slot 704 in the slot grouping 2 706 b may have adifferent depth. Slot grouping 2 706 b may be spaced apart from slotgrouping 1 706 a by a predetermined spacing. The predetermined spacingmay be a sufficient distance to allow a further slot grouping 706 to becut out in between slot grouping 1 706 a and slot grouping 2 706 b. Thismay permit motor units 712 to be interleaved.

In some cases, the slot groupings may be formed at differentpredetermined angles and the motor units may be inserted into the slotgroupings in either an interleaved or individually separated andadjacent manner. In other cases, the slot groupings may be adjacent andmay be configured to receive separated or interleaved motor units.

At 1408, a determination is made as to whether there are remaining slotgroupings 706 to be cut out of the exterior edge of the curvilinearlamination portion 702. In a particular case, there are remaining slotgroupings 706 to be cut out if there are regions of the exterior edge ofthe curvilinear lamination portion 702 without slots 704 cut out.

If there are remaining slot groupings 706 to be cut out, a new slotgrouping 1 706 a is cut out at 1404. In a particular case, the new slotgrouping 1 706 a may be located in between the previously cut out slotgrouping 1 706 a and slot grouping 2 706 b. Then at 1406, a new slotgrouping 2 706 b is cut out to the side of either the previously cut outslot grouping 1 706 a or previously cut out slot grouping 2 706 b.

If there are no remaining slot groupings 706 to be cut out, at 1410, adetermination is made as to whether there are remaining curvilinearlamination portions 702 to be formed. In a particular case, there areremaining curvilinear lamination portions 702 to be formed if the totalheight of the already formed curvilinear lamination portions 702 is apredetermined height. In some cases, the predetermined height may beequivalent or greater to the height of the motor unit 712.

If there are remaining curvilinear lamination portions 702 to be formed,a curvilinear lamination portion 702 is formed at 1402. The newcurvilinear lamination portion 702 will have approximately the sameshape and the same slot groupings cut out as the previously formedcurvilinear lamination portion 702.

If there are no remaining curvilinear lamination portions 702 to beformed, at 1412, the curvilinear lamination portions 702 are stackedinto a curvilinear lamination stack 708. The curvilinear laminationportions 702 are attached to each other to form the curvilinearlamination stack 708 using a suitable glue, epoxy, or the like.

At 1414, the motor units 712 are inserted straight into the slotgroupings 706 such that sides of the motor unit 712 are inserted into aslot grouping 706 pair (slot grouping 1 706 a and slot grouping 2 706b).

FIG. 15 illustrates a flowchart for a method 1500 of laying out sensorson a curvilinear track section, according to an embodiment. At 1502, thelength and width of the extension 118 of the moving element 104 isdetermined. In some cases, the extension 118 may be approximately thesame width as the moving element 104.

At 1504, a determination is made as to the initial layout of the sensors1008 on the curvilinear track section 1000 using the width of theextension 118 as a guide. The extension 118 may have a predeterminedsensor coverage over the sensors as the moving element 104 traverses thecurvilinear track section 1000. In a particular case, the predeterminedsensor coverage is such that the extension 118 covers at least twosensors 1008 at a given time. In this case, the spacing between twosensors should be less than the length of the extension 118. In somecases, there may be two rows of offset sensors 1008, an inner row ofsensors 1008 a and an outer row of sensors 1008 b. In these cases, theextension 118 may cover two sensors 1008 from both rows at a given time.In other cases, the predetermined sensor coverage may be configured suchthat there is adequate overlap of two sensors 1008 for handoff from onesensor 1008 to the other sensor 1008.

At 1506, the initial layout is tested by passing an extension 118 overthe sensors 1008 positioned in the initial sensor layout. At 1508, adetermination is made as to whether the test met the predeterminedsensor coverage; such as whether the extension 118 covered at least twosensors 1008 at appropriate timings for the duration of the movingelement's 104 traversal of the curvilinear track section 1000. In somecases, the testing may be accomplished virtually, for example, with a 3DCAD simulation.

At 1510, if the test met the predetermined sensor coverage, the sensors1008 are installed on the curvilinear track section 1000. At 1512, ifthe test did not meet the predetermined sensor coverage, the layout ofthe sensors 1008 is adjusted. In an example, if at one point in thetrack the extension 118 only covered one sensor 1008, the sensor 1008spacing is shortened to ensure dual sensor 1008 coverage of theextension 118. The rest of the sensors 1008 may also be shiftedaccordingly. Sensors 1008 may also be added or removed as required.Then, at 1506, the new sensor 1008 layout is tested. In other cases, thepredetermined sensor coverage may be configured such that there isadequate overlap of two sensors 1008 for handoff from one sensor 1008 tothe other sensor 1008.

FIG. 16 illustrates a flowchart for a method 1600 of linearizing sensorson a curvilinear track section, according to an embodiment. At 1602, thelocation of the first sensor 1008 of the curvilinear track section 1000is configured such that the extension 118 of the moving element 104 canoverlap the first sensor 1008 and the last sensor 122 or 123 of anadjacent straight section 102 of track at the same time. The area wherethe extension overlaps both sensors 1008 and 122 or 123 may be calledthe “overlap region”.

At 1604, a moving element 104 with the extension 118 is passed throughthe overlap region. While the moving element is in the overlap region, amoving element 104 velocity reading is read from both the last sensor122 or 123 of the straight section 102 and the first sensor 1008 of thecurvilinear track section 1000. At 1606, the difference in the readingsfrom the sensors 1008, 122, 123 is determined.

At 1608, the difference in the readings is used to adjust the sensorreading from the first sensor 1008 of the curvilinear track section1000. In adjusting the readings from the first sensor 1008 of thecurvilinear track section 1000, a predetermined position table may beused. In an example, the last sensor 122 or 123 of the straight section102 indicates the moving element 104 is moving at 0.200 m/sec, apredetermined position table may be used for the first sensor 1008 ofthe curvilinear track section 1000 such that the readings coming fromthe first sensor 1008 of the curvilinear track section 1000 are adjustedto match the 0.200 m/sec.

At 1610, the position adjustment determined at 1608 may be used toadjust the other sensors 1008 around the curvilinear track section 1000.Again, in adjusting the readings from the other sensors 1008 of thecurvilinear track section 1000, a predetermined position table may beused.

FIG. 17 illustrates a flowchart for a method 1700 of moderating magneticgap on a curvilinear track section, according to an embodiment. Anincrease in magnetic gap may be formed as the moving element 104traverses through the curvilinear track section 1000. The magnetic gapis the distance between the magnets of the moving element 104 and thecurvilinear track section 1000. The magnetic gap may increase as themoving element 104 traverses through the curvilinear track section 1000until the magnetic gap may be at its greatest at the apex of thecurvilinear track section 1000. A magnetic gap may have unwanted effectsas it may reduce the magnetic coupling of the moving element 104 to thecurvilinear lamination stack 708. At 1702, the size of the magnetic gapis determined.

Due to this gap, a boost in current to the motor coil 714, resulting inmore thrust on the moving element 104, may be applied as the movingelement 104 approaches and traverses through the region of greatestmagnetic gap. The boost in current, and thus thrust, may eliminate thegap by increasing the magnetic field between the moving element 114 andthe curvilinear track section 1000. A boost may be applied at anysuitable scale factor of current, for example, 1.5 times, 2.0 times, orthe like. At 1704, the appropriate scale factor of boost is determined.The appropriate scale factor may, at least partially, overcome themagnetic gap at the region of greatest magnetic gap.

At 1706, the zone controller 602 is configured to apply the scale factordetermined at 1704 when the moving element is at the region of greatestmagnetic gap, typically when the moving element 104 is at the apex ofcurvilinear track section 1000. The zone controller 602 is alsoconfigured to provide the least boost, or no boost, when the movingelement 104 is at either end of the curvilinear track section 1004. Inbetween the ends and the apex of the curvilinear track section 1000, thezone controller 602 may be configured to apply a gradual gradient ofboost or a stepped gradient of boost starting from the lowest boost atthe ends of the curvilinear track section 1000 to the greatest boost atthe apex of the curvilinear track section 1000.

In the preceding description, for purposes of explanation, numerousdetails are set forth in order to provide a thorough understanding ofthe embodiments. However, it will be apparent to one skilled in the artthat these specific details may not be required. In other instances,well-known structures and circuits are shown in block diagram form inorder not to obscure the understanding. For example, specific detailsare not provided as to whether the embodiments described herein areimplemented as a software routine, hardware circuit, firmware, or acombination thereof.

Embodiments of the disclosure or elements thereof can be represented asa computer program product stored in a machine-readable medium (alsoreferred to as a computer-readable medium, a processor-readable medium,or a computer usable medium having a computer-readable program codeembodied therein). The machine-readable medium can be any suitabletangible, non-transitory medium, including magnetic, optical, orelectrical storage medium including a diskette, compact disk read onlymemory (CD-ROM), memory device (volatile or non-volatile), or similarstorage mechanism. The machine-readable medium can contain various setsof instructions, code sequences, configuration information, or otherdata, which, when executed, cause a processor to perform steps in amethod according to an embodiment of the disclosure. Those of ordinaryskill in the art will appreciate that other instructions and operationsnecessary to implement the described implementations can also be storedon the machine-readable medium. The instructions stored on themachine-readable medium can be executed by a processor or other suitableprocessing device, and can interface with circuitry to perform thedescribed tasks.

The above-described embodiments are intended to be examples only.Alterations, modifications and variations can be effected to theparticular embodiments by those of skill in the art without departingfrom the scope, which is defined solely by the claims appended hereto.

We claim:
 1. A method for manufacturing a curvilinear track section of alinear motor system, the method comprising: forming a curvilinear trackportion into a suitable shape; cutting out a first slot grouping from anexterior edge of the curvilinear track portion, wherein the first slotgrouping is at a first predetermined angle relative to the exterior edgeof the curvilinear track portion; cutting out a second slot groupingfrom the exterior edge of the curvilinear track portion, wherein thesecond slot grouping is at a second predetermined angle relative to theexterior edge of the curvilinear track portion; and inserting motorunits into the first and second slot groupings.
 2. The method of claim 1wherein each of the first and second slot groupings comprise pairs ofslot groupings and the pairs of slot groupings interleave.
 3. The methodof claim 1 wherein the curvilinear track portion and the first andsecond slot groupings are configured to provide a sinusoidal angularvelocity profile for moving elements on the curvilinear track section.4. The method of claim 1 wherein the curvilinear track portion has atleast one region with a clothoid profile.
 5. The method of claim 1wherein the cutting out of the first group of slots and the second groupof slots is by stamping, laser cutting, or water jet cutting.
 6. Themethod of claim 1 wherein slots within each slot grouping have differentslot depths.
 7. The method of claim 6 wherein the depth of each slotdepends on the angle of the slot relative the exterior edge of thecurvilinear track portion.
 8. The method of claim 6 wherein the depth ofthe slot is configured to receive a motor unit.
 9. The method of claim 6wherein the depth of the slot on one end of the first slot grouping andthe depth of the slot on another end of the first slot grouping areapproximately equal to the depth of a straight section of the linearmotor system and the depths of the slots in between are deeper.
 10. Acurvilinear track section of a linear motor system comprising: acurvilinear track portion having a predetermined curved shape; a firstslot grouping formed in an exterior edge of the curvilinear trackportion, wherein the first slot grouping is at a predetermined anglerelative to the exterior edge of the curvilinear track portion; a secondslot grouping formed in the exterior edge of the curvilinear trackportion, wherein the second slot grouping is at a second predeterminedangle relative to the exterior edge of the curvilinear track portion;and motor units inserted into the first and second slot groupings. 11.The curvilinear track section of claim 10 wherein each of the first andsecond slot groupings comprise pairs of slot groupings and the pairs ofslot groupings interleave.
 12. The curvilinear track section of claim 10wherein the curvilinear track portion and the first and second slotgroupings are configured to provide a sinusoidal angular velocityprofile for moving elements on the curvilinear track section.
 13. Thecurvilinear track section of claim 10 wherein the curvilinear trackportion has at least one region with a clothoid profile.
 14. Thecurvilinear track section of claim 10 wherein slots within each slotgrouping have different slot depths.
 15. The curvilinear track sectionof claim 14 wherein the depth of the slot depends on the angle of theslot relative the exterior edge of the curvilinear track portion. 16.The curvilinear track section of claim 14 wherein the depth of the sloton one end of the first slot grouping and the depth of the slot onanother end of the first slot grouping are approximately equal to thedepth of a straight section of the linear motor system and the depths ofthe slots in between are deeper.
 17. The curvilinear track section ofclaim 14 further comprising a plurality of sensors positioned on thecurvilinear track section, wherein the sensors are orientedperpendicular to the direction of motion.
 18. The curvilinear tracksection of claim 17 wherein a first sensor of the plurality of sensorsis calibrated based on the calibration of a last sensor on a straighttrack portion immediately preceding the curvilinear track selection. 19.The curvilinear track section of claim 17 further comprising: acontroller configured to provide a boost to a selected motor unit when amoving element approaches an apex of the curvilinear track section. 20.A wedge aligner for a linear motor system, the wedge aligner comprising:a fixed mount configured to rigidly attach to a first track section ofthe linear motor system and flexibly attach to a second track section; awedge configured be inserted between the flexibly attaching portion ofthe fixed mount and the second track section; and an adjustor providedto the wedge configured to translate the wedge back and forth along thelongitudinal axis of the first and second track sections in order tocompensate for stack-up tolerances.